The goal of this application is to define a translational platform of candidate biomarkers for Alopecia Areata (AA). AA is one of the most common autoimmune diseases, with a lifetime risk of approximately 2%, affecting 5.3 million individuals in the United States alone, including males and females of all ages and ethnic groups. Autoimmunity is acquired against the hair follicles in the skin, which causes hair loss associated with an accumulation of immune-response cells around the affected hair follicles. The prognosis of AA is unpredictable and currently there is no definitive treatment. The chronic nature of this disease profoundly impacts patients. A dearth of information about the underlying pathology has been the major obstacle in identifying effective treatments. In 2000, NIH/NIAMS funded the National Alopecia Areata for the registration and data collection of individuals with a confirmed diagnosis of AA and their family members. For the purpose of this Ancillary Studies application, we require both fresh tissue biopsies as well as freshly-collected blood samples from a subset of 60 subjects. Therefore, it is essential that this grant be carried out in parallel with the NAAR contract. We will develop a translational platform for AA by characterizing the genetic networks of two interacting tissues in the context of an autoimmune disease: cells of the immune system as well as the skin. Translational advances in AA will likely have broad impact in autoimmunity. Our recent GWAS study in AA unexpectedly revealed a number of risk loci shared by rheumatoid arthritis (RA), type 1 diabetes (T1D), celiac disease (CeD), SLE, MS and psoriasis (PS). The commonality with RA, T1D, and CeD is especially noteworthy in light of the shared pathogenic expression of NK ligands in the target organ of each of these three autoimmune diseases. Thus, pursuit of biomarker development in AA, by integrating signatures in the blood and the target organ, could accelerate candidate biomarker discovery for other related autoimmune states in which the target organ is not as accessible. Importantly, these studies will provide the basis for a translational platform in AA; to identify molecular drivers of AA subtypes enabling drug development to be appropriately targeted and monitored in this disease.